425
FXUS02 KWBC 250700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EST FRI NOV 25 2022
VALID 12Z MON NOV 28 2022 - 12Z FRI DEC 02 2022
...SNOW LIKELY ACROSS HIGHER ELEVATIONS OF THE WEST INTO NEXT
WEEK...
...HEAVY RAIN AND SEVERE WEATHER POSSIBLE ACROSS PARTS OF THE
SOUTH AND INTO THE OHIO VALLEY TUESDAY-WEDNESDAY NEXT WEEK...
..OVERVIEW
LATEST GUIDANCE AGREES FAIRLY WELL FOR THE LARGE SCALE PATTERN
THAT SHOULD FEATURE MEAN TROUGHING OVER THE WEST AND AN INITIAL
BAHAMAS/CUBA UPPER RIDGE ULTIMATELY BUILDING WESTWARD OVER THE
GULF OF MEXICO. WITHIN THIS PATTERN, FEATURES ACROSS THE LOWER 48
SHOULD BE PROGRESSIVE. LEADING NEW ENGLAND LOW PRESSURE AND
TRAILING FRONT SHOULD QUICKLY DEPART AFTER EARLY MONDAY. THEN
WESTERN-CENTRAL U.S. TROUGH ENERGY DURING THE FIRST HALF OF THE
WEEK SHOULD SPREAD RAIN AND MOUNTAIN SNOW ACROSS THE NORTH-CENTRAL
WEST COAST INTO CENTRAL ROCKIES, AND THEN SUPPORT DEEPENING
SURFACE LOW PRESSURE THAT TRACKS FROM THE CENTRAL PLAINS INTO THE
GREAT LAKES TUESDAY-WEDNESDAY. THE TRAILING COLD FRONT MAY FOCUS
HEAVY RAINFALL FROM THE SOUTH INTO THE OHIO VALLEY, WITH SEVERE
WEATHER ALSO POSSIBLE OVER SOUTHERN AREAS, WHILE SOME SNOW WILL BE
POSSIBLE NORTH/WEST OF THE LOW TRACK. ANOTHER SYSTEM MOVING INTO
THE WEST DURING THE LATTER HALF OF THE WEEK SHOULD SPREAD
PRECIPITATION SOUTHEASTWARD ACROSS THE REGION. THE OVERALL PATTERN
WILL FAVOR BELOW NORMAL TEMPERATURES OVER MUCH OF THE WEST AND
PARTS OF THE HIGH PLAINS, WITH MONTANA AND NEARBY AREAS LIKELY TO
SEE THE MOST PERSISTENT AND COLDEST ANOMALIES.
..GUIDANCE AND PREDICTABILITY ASSESSMENT
THE FIRST PRIMARY FORECAST ISSUE INVOLVES THE COMBINATION OF
TROUGH ENERGY REACHING THE WEST EARLY IN THE WEEK AND A SMALL
UPPER LOW FARTHER EAST NEAR THE CANADIAN BORDER (WITH ITS OWN
SURFACE SYSTEM), WITH SUBTLE DETAILS HAVING A MEANINGFUL IMPACT ON
THE DEPTH AND TRACK OF CENTRAL PLAINS THROUGH GREAT LAKES LOW
PRESSURE TUESDAY-WEDNESDAY. LATEST GFS RUNS INCLUDING THE NEW 00Z
VERSION ARE ON THE WEAKER SIDE WHILE PASSING THROUGH THE GREAT
LAKES BUT EVENTUALLY STRENGTHEN MORE OVER CANADA. UKMET RUNS ARE
ON THE DEEP SIDE OF THE SPREAD, ABOUT 20 MB STRONGER THAN THE GFS
AS OF 12Z WEDNESDAY. MOST 00Z GEFS MEMBERS ARE DEEPER THAN THE
OPERATIONAL RUN WHILE THE 00Z GFS PARALLEL IS ACTUALLY IN THE
DEEPER HALF AND NORTHWEST SIDE OF THE ENVELOPE. THE IMPORTANT
DETAILS ARE SUFFICIENTLY SMALL IN SCALE TO HAVE LOW PREDICTABILITY
SEVERAL DAYS OUT IN TIME SO AN INTERMEDIATE APPROACH FOR DEPTH AND
TRACK APPEARS REASONABLE AT THIS TIME. THIS WAS ACHIEVED BY AN
OPERATIONAL MODEL COMPOSITE AS THE STARTING POINT FOR THE FORECAST
INTO EARLY DAY 5 WEDNESDAY.
NOT SURPRISINGLY GIVEN THE MORE DISTANT TIME FRAME, THERE HAS BEEN
SOMEWHAT MORE MODEL SPREAD AND RUN-TO-RUN VARIABILITY FOR DETAILS
OF THE NEXT INDIVIDUAL TROUGH FORECAST TO DIG INTO THE WEST DURING
THE LATTER HALF OF THE WEEK. CMC RUNS HAVE BEEN MORE PRONOUNCED
WITH AN UPSTREAM SHORTWAVE THAT COULD LEAD TO A MORE PROGRESSIVE
WESTERN TROUGH BUT FOR NOW THIS SCENARIO IS IN THE MINORITY.
TRENDING THE FORECAST TO AN EVEN BLEND OF THE 18Z GFS/12Z ECMWF
AND THEIR ENSEMBLE MEANS BY DAY 7 FRIDAY PROVIDED A REASONABLE
ACCOUNT FOR THE DETAIL UNCERTAINTIES AT THAT TIME FRAME.
..WEATHER/HAZARD HIGHLIGHTS
EXPECT THE WESTERN U.S. TO SEE TWO PRIMARY PRECIPITATION EVENTS
NEXT WEEK. THE FIRST SHOULD SPREAD RAIN AND MOUNTAIN SNOW FROM
PARTS OF THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA THROUGH THE
GREAT BASIN AND CENTRAL ROCKIES MONDAY-TUESDAY, WITH HIGHEST
TOTALS OVER FAVORED TERRAIN FROM THE OREGON CASCADES INTO THE
CENTRAL THIRD OF THE ROCKIES. THE NEXT AREA OF MOISTURE SHOULD
ARRIVE INTO THE PACIFIC NORTHWEST ON TUESDAY AND THEN EXPAND
STEADILY SOUTHEASTWARD ACROSS THE WEST THROUGH THE REST OF THE
WEEK. SOME PRECIPITATION MAY BE ON THE LOCALLY MODERATE TO HEAVY
SIDE OVER THE PACIFIC NORTHWEST TUESDAY-WEDNESDAY, WITH DECLINING
CONFIDENCE IN THE COVERAGE AND INTENSITY ELSEWHERE LATER IN THE
WEEK DUE TO UNCERTAINTY IN UPPER TROUGH DETAILS. SNOW LEVELS IN
THE NORTHWEST COULD REACH DOWN TO FAIRLY LOW ELEVATIONS TOWARD THE
END OF THE WEEK.
DURING TUESDAY-WEDNESDAY, STRENGTHENING CENTRAL PLAINS INTO GREAT
LAKES LOW PRESSURE AS WELL AS ITS TRAILING COLD FRONT PLUS A
SEPARATE WARM FRONT LIFTING THROUGH GULF OF MEXICO WILL LIKELY
BRING PRECIPITATION TO MUCH OF THE EASTERN HALF OF THE LOWER 48.
WIDESPREAD AND POTENTIALLY HEAVY RAINFALL IS POSSIBLE FROM THE
LOWER MISSISSIPPI VALLEY INTO THE SOUTHERN APPALACHIANS AND
POTENTIALLY SOME LOCATIONS FARTHER NORTH AS WELL. SUFFICIENT
MOISTURE AND INSTABILITY IN THE WARM SECTOR COULD ALSO LEAD TO
SEVERE WEATHER, WITH THE STORM PREDICTION CENTER ALREADY
HIGHLIGHTING THE CHANCE IN THEIR OUTLOOK FOR NEXT TUESDAY ACROSS
PARTS OF EASTERN TEXAS INTO THE LOWER MISSISSIPPI VALLEY. THERE
ALSO REMAINS POTENTIAL FOR SNOW TO THE NORTHWEST OF THE SURFACE
LOW TRACK WITH A POSSIBLE FOCUS OVER THE UPPER MIDWEST. DETAILS ON
THIS SNOW POTENTIAL WILL BECOME BETTER DEFINED ONCE GUIDANCE SHOWS
BETTER CLUSTERING FOR TRACK AND DEPTH. FINALLY, THIS STORM MAY
PRODUCE STRONG WINDS OVER SOME AREAS.
MUCH OF THE WEST AND PORTIONS OF THE HIGH PLAINS SHOULD SEE BELOW
NORMAL TEMPERATURES FOR MOST OF NEXT WEEK. COLDEST ANOMALIES WILL
GENERALLY CORRESPOND TO THE TWO PRIMARY UPPER TROUGHS AFFECTING
THE REGION, ESPECIALLY ON TUESDAY AND FRIDAY WHEN THE GREATEST
COVERAGE OF HIGHS 20-30F BELOW NORMAL IS LIKELY OVER MONTANA AND
ALSO FARTHER SOUTH/SOUTHEAST ON TUESDAY. EXPECT HIGHS 10-20F BELOW
NORMAL OVER THE INTERIOR WEST ON TUESDAY AND THE NORTHWEST/GREAT
BASIN ON FRIDAY. MEANWHILE, THE SOUTH-CENTRAL AND EAST-CENTRAL
U.S. WILL LIKELY SEE A BRIEF PERIOD OF ABOVE NORMAL TEMPERATURES
(UP TO PLUS 10-15F ANOMALIES FOR HIGHS AND SLIGHTLY WARMER FOR
MORNING LOWS) ON TUESDAY-WEDNESDAY AHEAD OF THE SYSTEM EMERGING
FROM THE WEST/PLAINS. THEN THE COLD AIR BEHIND THE FRONT WILL DROP
READINGS OVER MOST OF THESE AREAS TO BELOW NORMAL BY NEXT THURSDAY.
RAUSCH
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES ARE
AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML
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